Mechanically alloyed NiCuMnWX (X = Co, Fe, or Mo) high-entropy alloy electrocatalysts for alkaline water splitting

Abstract

High-entropy alloys have great potential as electrocatalysts for water-splitting reactions. Benefiting from the cocktail effect and lattice distortion, high-entropy alloys exhibit relatively low overpotentials and significant stability, making them excellent candidates for electrocatalytic water splitting. These materials offer a cost-effective and abundant alternative to conventional noble-metal catalysts such as Pt and IrO₂, which are limited by high costs and scarcity. This study investigates the electrocatalytic performance of high-entropy alloy powders prepared with equimolar ratios of Ni, Cu, Mn, and W, with additional elements (Co, Fe, or Mo) introduced to optimize their activity for the hydrogen evolution reaction and oxygen evolution reaction. The high-entropy alloy powders are synthesized via ball milling, involving both dry milling and wet milling in ethanol, followed by washing and drying at room temperature. Comprehensive characterization techniques, including X-ray diffraction, field-emission scanning electron microscopy, scanning transmission electron microscopy with energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy, are employed to analyze their structure and properties. Electrochemical studies reveal that Fe and Mo significantly enhance hydrogen evolution reaction activity, achieving overpotentials of 301 mV and 305 mV, respectively, with corresponding Tafel slopes of 200.9 mV dec⁻¹ and 153.3 mV dec⁻¹. Meanwhile, Co incorporation improves oxygen evolution reaction performance, reducing the overpotential to 326 mV with a Tafel slope of 143.7 mV dec⁻¹. These findings underscore the potential of high-entropy alloy powders for advancing renewable energy technologies.